1. Field of the Invention
The present invention relates to a broad band signal spaced coupling device, and more particularly to a device which comprises a cross point matrix whose switching matrix elements are respectively controlled by a decoder-controlled, cross point-associated memory cell which are respectively formed with a complementary metal-oxide-semiconductor transfer gate, the useful signal input of every such transfer gate being preceded by a complementary metal-oxide-semiconductor inverter.
2. Description of the Prior Art
Recent developments in telecommunications technology have led to service intergrating communications transmission and switching systems for narrow band and broad band communications services which provide light wave guides as the transmission medium in the area of the subscriber lines by way of which both the narrow band communications services such as, in particular, 64-kbit/s digital telephony, as well as broadband communication services, such as, in particular, 140-Mbit/s picture telephony, are conducted, whereby, however, a narrow band signal switching devices and broad band signal switching devices are provided in the switching centers (preferably having shared control devices) such as disclosed in the German patent 24 21 002.
In conjunction with a broad band time-division multiplex switching matrix device whose cross points are used in time-division multiplex for a respective plurality of connections, it is known in the art to connect two respective lines with the assistance of a gate element which is switched on and off by a cross point associated memory cell formed as a bi-stable D-flip-flop, whereby the cross point-associated memory cell whose clock input is supplied with an appropriate clock signal, is driven in only one coordinate direction, and particular, at its D-input (Pfannschmidt, "Arbeitsgeschwindigkeits-grenzen von Koppelnetzwerken fuer Breitband-Digitalsignale", dissertation, Braunschweig, 1978, FIG. 6.7). In view of the time-division multiplex factor of about 4-8, which can be achieved given a bit rate of 140 Mbit/s and in view of the involved circuit technology required, exclusive space-coupling devices are, however, currently preferred for switching broad-band signals, the connections being made by way of the individual cross points being separated from one another only in terms of space.
An exclusive broad band signal space coupling device can be constructed as a cross point matrix in whose cross points the switching elements are respectively controlled by a decoder-controlled, cross point-associated holding memory cell (see Pfannschmidt, op. cit., FIG. 6.4; Electronics, Dec. 15, 1983, pp. 88-89); the switching elements can thereby be respectively constructed as CMOS transfer gates (ISS'84 Conference Papers 23Cl, FIG. 9). The utilization of a simple CMOS transfer gate as a switching element, however, is connected, given the through-connected condition, with a load of its input line due to the capacitance of its output line, this circumstances producing signal delays; as a consequence of what are referred to as under-threshold effects (for example, in the form of stray currents or under threshold currents), along the MOS transistors, moreover, cross talk phenomena occur across switching matrix elements located in their inhibited condition can occur.